The term "molecular sieve" has been used to describe materials which may be used to separate components of a mixture on the basis of molecular size and shape, and has been used in conjunction with such materials as silicas, metalloaluminates, and aluminophosphates, as well as with other materials having a regular framework structure suitable for such separation. See, e.g., R. Szostak, Molecular Sieves, Principles of Synthesis and Identification, Van Nostrand Reinhold, New York, 1989, pages 2-6. Szostak (supra) at page 3-4 provides a list of elements that may form molecular sieve framework structures in place of aluminum or silicon. However, no mention is made of any particular molecular sieve material in which all of the silicon and aluminum is replaced by other elements, and no directions are provided for making such a material. However, see Szostak, (supra) Ch. 4, for a listing and discussion of such molecular sieves that have been made.
Zeolites, and zeolite-like materials, sometimes also called molecular sieves, are well known in the art. By far the most common of these materials are the framework aluminosilicates, which occur naturally, and are also made by synthetic methods. Certain elements, such as boron, gallium, germanium, phosphorous, titanium, beryllium, zinc, and others have been substituted in part, or less commonly, in whole for either the silicon or aluminum in zeolite and zeolite-like structures. See, e.g., R. Szostak, supra, Ch. 4., pages 205-281. In addition to the silicon and aluminum that compositionally define the zeolite molecular sieves, other cations (which need not be isoelectronic with silicon or aluminum) can also occupy framework sites.
U.S. Pat. No. 4,329,328 describes the preparation of a molecular sieve containing a "sodium zinco/stanno/titano-silicate", which can be thought of as a zeolite in which the aluminum has been substituted for by zinc, tin or titanium. U.S. Pat. No. 4,670,617 describes a molecular sieve material containing zinc but no aluminum. The molecular sieve materials of these patents contain substantial amounts of silicon.
U.S. Pat. No. 4,440,871 and U.S. Pat. No. 4,310,440 describe molecular sieve materials in which phosphorous has been respectively substituted for some or all of the silicon in zeolite-like materials. Substantial amounts of aluminum are present in these compositions.
Much less common are molecular sieves in which all, or almost all of the silicon and aluminum have been substituted for by other elements. R. C. Rouse, et. al., Neues Jahr. Mineral. Monatsh. pages 433-440 (1987), report the discovery of a naturally occurring "zeolite" which contains beryllium and phosphorous, and no silicon or aluminum. G. Harvey and W. M. Meier in P. A. Jacobs and R. A. van Santen, Eds., Studies in Surface Science and Catalysis, Vol. 49, Zeolites: Facts, Figures, Future, Part. A. Proc. of the 8th Int. Zeolite. Conf., Amsterdam, Jul., 1989, Elsevier, Amsterdam, 1989, pages 411-420, report the synthesis of several zeolite-type materials containing beryllium and phosphorous, but no aluminum or silicon. These materials were prepared by hydrothermal methods at temperatures of 100.degree.-200.degree. C.
It is well known in the art that molecular sieves are useful for ion exchange, drying, catalysis, and purification and separation of various compounds.